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Tunable white-light emission from Pr3+/Dy3+ co-doped B2O3 - TeO2 PbO - ZnO Li2O - Na2O glasses
摘要： In this paper, structural and optical analysis of boro-tellurite based glasses co-doped with Dy3+ and Pr3+ ions has been carried out. The glasses were fabricated by traditional melt quenching technique. XRD results confirm the amorphous-like nature of the glasses. FTIR spectroscopy was applied to explore the functional groups and interactions for the samples. The transition temperatures of glasses were identified by TGA/DSC analysis. Optical absorption and emission spectra of all the glasses have been recorded in the UVe Vis- NIR spectral range. Tauc's method was applied to determine the direct and indirect optical band gaps. Luminescence spectra show intense emission bands at ～482 nm and ～574 nm wavelengths under λexc = 388 nm corresponding to Dy3+: 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions. Decay time data revealed the occurrence of a non-radiative energy transfer from Dy3+ to Pr3+ ions. Intense emission bands are identified at ～602 nm (orange), ～487 nm (blue) and ～574 nm (yellow) observed upon λexc = 437 nm, corresponding to Pr3+:1D2→3H4, Pr3+:3P0,1,2 → 3H4/Dy3+: 4F9/2 → 6H13/2 and Dy3+: 4F9/2 → 6H13/2 transitions, respectively, where the Dy3+ emissions are due to energy transfer from Pr3+ to Dy3+ ions. The CIE chromaticity results confirm that different colors can be generated by tuning the exciting wavelength, where all the glasses are capable to emit white light under λexc = 388 nm, while at λexc = 437 nm the samples (S2eS4) emit reddish orange light. Accordingly, it is plausible to suggest these glasses for white LED and SSL applications.
关键词： Optical absorption,Photoluminescence,W-LEDs,Raman spectroscopy,Borotellurite glass,Energy transfer
更新于2025-09-23 15:23:52
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Ultrasensitive analysis of kanamycin residue in milk by SERS-based aptasensor
摘要： An ultrasensitive method for the kanamycin (KANA) detection in milk sample using surface-enhanced Raman spectroscopy-based aptasensor was employed in the current study. Double strand DNA binding bimetallic gold@ silver nanoparticles were developed as a sensing platform. Probe DNAs were first embedded on the surface of gold nanoparticles by the end-modified thiol, and after silver shell encapsulating, KANA aptamer DNAs with the Raman reporter Cy3 were then hybridized with probe DNAs by complementary base pairing. Results showed that with increase in the KANA concentration, the Raman intensity of Cy3 decreased. Besides achieving selectivity, an ultralow detection limit of 0.90 pg/mL, a broad linear relationship ranging from 10 μg/mL to 100 ng/mL in aqueous reagent and satisfactory recoveries of 90.4–112% in liquid whole milk were obtained. The result of actual sample proved that this aptasensor was promising in trace determination of KANA residue.
关键词： Milk,Kanamycin,Aptamer,Surface enhanced Raman spectroscopy
更新于2025-09-23 15:23:52
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Performance anaysis and small signal identification of time-resolved stand-off Raman spectroscopy system
摘要： Performance anaysis and small signal identification of time-resolved stand-off Raman spectroscopy system. Over the last decade, the time-resolved stand-off Raman spectroscopy has attracted considerable attention due to its daytime measurement model and fluorescent suppression. Suffering from the small Raman scattering efficiency, this system perusing large detection distance requires both large power consumption and optical system, which blocks its applications. In order to seek for high signal collection efficient, in this work, we designed a 2-inch refractive telescope system, and obtained 20 m detection distance using a frequency-doubled 532 nm Nd: YAG laser with pulse energy of 30 mJ. By adjusting the excitation energy through a variable attenuator, we investigate the interrelations of input power, the signal and the noise consisting of the internal and signal-induced noises. For both main peak and sub peak, the signal-induced noises are subject to a power function of the signal intensity, and can be filtered and smoothed by the norm-distribution-function weighted moving average method (WMAM) without the loss of the signal information. After transforming the correlation spectrum, defined by the multiplication of the noise and signal spectrum, iteratively by WMAM, we can identify the small signal of about 1 count beyond the internal noise limitation. With help of the iteration method, the requirement of integration time as well as the excitation energy can be greatly reduced.
关键词： small signal,Raman spectroscopy,stand-off
更新于2025-09-23 15:23:52
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Shining light on growth-dependent surface chemistry of organic crystals: a polarised Raman spectroscopic and computational study of aspirin
摘要： Understanding and controlling crystal surfaces is a critical problem in contemporary materials science. Organic crystal surfaces present the additional complexity of multiple terminations with different functional groups. These alternate terminations influence the surface chemistry and exert control on many material properties. While established tools for surface characterization exist, few provide the chemical information required to unambiguously identify functional groups. Polarized Raman spectroscopy is a versatile tool that can provide detailed chemical information on molecular materials, and, when used in a microscope configuration, can be used to map substrates on a micron scale. In this work, we demonstrate the use of polarized Raman to study the surface chemistry of aspirin. By analyzing crystals grown under a variety of conditions, we relate the growth solvent to the surface termination and reconcile the conflicting results in the literature on the nature of the <100> surface. Our results are supported by detailed first-principles modelling of the surfaces and their vibrational spectra. This study establishes the potential of polarized Raman microscopy as a tool for organic surface science that, when combined with predictive modelling, provides a powerful means to understand and ultimately control surface chemistry.
关键词： aspirin,first-principles modelling,crystal growth,polarized Raman spectroscopy,surface termination,lattice dynamics
更新于2025-09-23 15:23:52
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Microthermometry and Raman spectroscopy of fluid inclusions from El Vapor gold mineralizations, Colombia
摘要： Epigenetic El Vapor gold mineralization is hosted by the Segovia batholith and sedimentary rocks at both sides of El Nús fault, in the eastern flank of the Colombian Andes central cordillera. Gold mineralization is composed by continuous and discontinuous sigmoidal and stockwork veins and veinlets from a few centimeters to two meters of thickness and by hydrothermal breccias. Ore mineralogy includes Pyrite + Galena + Sphalerite + Chalcopyrite + Pyrrhotite + Proustite - Pyrargyrite. Gold occurs as inclusions within pyrite, between quartz crystals and filling fractures within pyrite at a late stage of mineralization. The fluid inclusions in quartz veins occur as clusters of primary inclusions or in alignments of secondary and pseudo-secondary inclusions. Based on petrography and Raman spectroscopy, four types of fluid inclusions could be recognized: (1) Type I are primary biphasic, liquid-rich, with CO2(v) + N2(v) + CH4(v) + KCl(AQ) + NaCl(AQ) + H2O(L), (2) Type II are primary or pseudo-secondary, multi-volatile presenting CO2(V) + CO2(L) + N2(V) + CH4(V) + KCl(AQ) + NaCl(AQ) + H2O(L), (3) Type III are secondary, two-phase, liquid-rich inclusions, composed of H2O(v) + H2O(L) + KCl(AQ) + NaCl(AQ) and have two different times of formation (IIIA and IIIB), (4) Type IV are very rare, three-phasic, secondary inclusions and composed of S + H2O(V) + H2O(L) + KCl(AQ) + NaCl(AQ). The microthermometric and spectroscopic analysis of fluid inclusions indicates that the fluid associated with the first event of mineralization identified in El Vapor have low to moderate salinities (3.5-9.2 wt% NaCl equiv.), with trapping temperatures between 214°C and 350°C and pressures between 0.5kbar and 2.9kbar. Due to the nonexistence of fluid inclusions with variable degree of filling with opposite homogenization and because of the variations of salinity in a restricted homogenization temperatures range, it is proposed an isothermal fluid mixture process, which together with fO2 changes, generated by fluid reaction with the carbonaceous shales of the Segovia sedimentary rocks, could influence the process of gold deposition. Hydrothermal fluids from El Vapor were near neutral and reduced; simlar features have been found in orogenic deposits hosted by turbidite sequences around the world.
关键词： Orogenic,reduced fluids,El Vapor district,Microthermometry,Raman spectroscopy,Gold mineralizations,Fluid inclusions
更新于2025-09-23 15:23:52
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Giant-Shell CdSe/CdS Nanocrystals: Exciton Coupling to Shell Phonons Investigated by Resonant Raman Spectroscopy
摘要： The interaction between excitons and phonons in semiconductor nanocrystals plays a crucial role in the exciton energy spectrum and dynamics, and thus in their optical properties. We investigate the exciton-phonon coupling in giant-shell CdSe/CdS core-shell nanocrystals via resonant Raman spectroscopy. The Huang-Rhys parameter is evaluated by the intensity ratio of the longitudinal-optical (LO) phonon of CdS with its first multiscattering (2LO) replica. We used four different excitation wavelengths in the range from the onset of the CdS shell absorption to well above the CdS shell band edge to get insight into resonance effects of the CdS LO phonon with high energy excitonic transitions. The isotropic spherical giant-shell nanocrystals show consistently stronger exciton-phonon coupling as compared to the anisotropic rod-shaped dot-in-rod (DiR) architecture, and the 2LO/LO intensity ratio decreases for excitation wavelengths approaching the CdS band edge. The strong exciton-phonon coupling in the spherical giant-shell nanocrystals can be related to the delocalization of the electronic wave functions. Furthermore, we observe the radial breathing modes of the GS nanocrystals and their overtones by ultra-low frequency Raman spectroscopy with nonresonant excitation, using laser energies well below the band gap of the heteronanocrystals, and highlight the differences between higher order optical and acoustic phonon modes.
关键词： Giant-shell nanocrystals,acoustic phonons,Dot-in-rods,Raman spectroscopy,Core-shell heterostructures,exciton-phonon coupling
更新于2025-09-23 15:23:52
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Probing Lithium Carbonate Formation in Trace-O <sub/>2</sub> -Assisted Aprotic Li-CO <sub/>2</sub> Batteries Using in Situ Surface-Enhanced Raman Spectroscopy
摘要： A trace O2-assisted aprotic Li-CO2 battery represents a promising approach for CO2 recycling. However, cathode passivation and large overpotential are frequently observed for current Li-CO2 batteries because of the insolubility and non-conductivity of the discharge product of lithium carbonate (Li2CO3). Toward maximizing the energy capabilities of the Li-CO2 electrochemistry, it is crucially important to have a fundamental understanding of the Li2CO3 formation mechanism in Li-CO2 batteries. In this report, the discharge reaction of a trace O2-assisted Li-CO2 battery has been interrogated with in-situ surface enhanced Raman spectroscopy (SERS). It was found that in high donor number (DN) solvents Li2CO3 formation proceeds primarily via an 'electrochemical solution route' with peroxodicarbonate (C2O6^2-) as the key intermediate; while in low DN solvents Li2CO3 forms via a chemical reaction of Li2O2 and CO2 on the cathode surface, namely a 'chemical surface route'. It is notable that during discharge the trace O2 acts as a 'pseudo-catalyst' to activate CO2 in high DN solvents, but not in low-DN solvents. The mechanistic study presented here will assist to tailor-design better electrolyte systems and enable more energetic electrochemistry operating far away from the poison of Li2CO3.
关键词： surface enhanced Raman spectroscopy,lithium carbonate,O2-assisted aprotic Li-CO2 battery
更新于2025-09-23 15:23:52
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Suitability of Raman Spectroscopy for Assessing Anisotropic Strain in Thin Films of Doped Ceria
摘要： A protocol for characterizing relaxation of anisotropic strain in thin films of 10 mol% Eu- or Sm-doped ceria is described. The method is based on comparison of Raman spectra and X-ray diffraction patterns from substrate-supported films, displaying in-plane compressive strain (initial state), with analogous data from 2 mm diameter self-supported films (i.e., membranes), prepared by partial substrate removal (final state). These membranes are found to be relaxed, i.e., approximately unstrained, but with increased unit cell volume. The effective (i.e., 2-state) Grüneisen parameter of the F2g Raman active mode for these films is calculated to be 0.4 ± 0.1, which is ≈30% of the literature value for the corresponding ceramics under isostatic pressure. On this basis, it is found that the observed red-shift of the F2g mode frequency following isothermal strain relaxation of the doped ceria thin films cannot be determined solely by the increase in average unit cell volume. The study presented here may shed light on the suitability of Raman spectroscopy as a technique for characterizing strain in lanthanide-doped ceria thin films.
关键词： doped ceria,Raman spectroscopy,Grüneisen parameter,anelastic relaxation
更新于2025-09-23 15:23:52
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Portable spectroscopic system for <i>in vivo</i> skin neoplasms diagnostics by Raman and autofluorescence analysis
摘要： This paper studies the applicability of a portable cost-effective spectroscopic system for the optical screening of skin tumors. In vivo studies of Raman scattering and autofluorescence of skin tumors with the 785 nm excitation laser in the near infrared region included malignant melanoma, basal cell carcinoma, and various types of benign neoplasms. The efficiency of the portable system was evaluated by comparison with a highly sensitive spectroscopic system and with the diagnosis accuracy of a human oncologist. Partial least square analysis of Raman and autofluorescence spectra was performed; specificity and sensitivity of various skin oncological pathologies detection varied from 78.9% to 100%. 100% accuracy of benign and malignant skin tumors differentiation is possible only with a combined analysis of Raman and autofluorescence signals.
关键词： autofluorescence,optical biopsy,portable spectroscopic equipment,skin neoplasms,melanoma,partial least square analysis,Raman spectroscopy,malignancy
更新于2025-09-23 15:23:52
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Phonon coherences reveal the polaronic character of excitons in two-dimensional lead halide perovskites
摘要： Hybrid organic–inorganic semiconductors feature complex lattice dynamics due to the ionic character of the crystal and the softness arising from non-covalent bonds between molecular moieties and the inorganic network. Here we establish that such dynamic structural complexity in a prototypical two-dimensional lead iodide perovskite gives rise to the coexistence of diverse excitonic resonances, each with a distinct degree of polaronic character. By means of high-resolution resonant impulsive stimulated Raman spectroscopy, we identify vibrational wavepacket dynamics that evolve along different configurational coordinates for distinct excitons and photocarriers. Employing density functional theory calculations, we assign the observed coherent vibrational modes to various low-frequency (?50 cm?1) optical phonons involving motion in the lead iodide layers. We thus conclude that different excitons induce specific lattice reorganizations, which are signatures of polaronic binding. This insight into the energetic/configurational landscape involving globally neutral primary photoexcitations may be relevant to a broader class of emerging hybrid semiconductor materials.
关键词： resonant impulsive stimulated Raman spectroscopy,polaronic character,two-dimensional perovskites,density functional theory,excitons,phonon coherences
更新于2025-09-23 15:23:52